Scientists have retrieved sonar images of an ancient coastline 550 feet below the surface of the Black Sea that are strong evidence that a sudden violent flood destroyed a fresh water oasis and inspired the story of Noah's Ark, a theory advanced by two oceanographers at Columbia.

Explorer Robert Ballard, who found the remains of the Titanic, led a research team this summer that discovered the ancient beach dated 7,500 years ago. That date supports the ideas of Walter Pitman and Bill Ryan, senior scientists at the Lamont-Doherty Earth Observatory, who believe that a flood 7,500 years ago forced the diaspora of an advanced civilization. Their research has generated new discussions about the role climate change has played in human history.

The story behind their discovery is recounted in "Noah's Flood: The New Scientific Discoveries About the Event That Changed History," which was published in 1999. The book sparked new archeological interest in the Black Sea, and inspired Ballard to look for further evidence to support their theories.

Ryan and Pitman believe that the sealed Bosporus strait, which acted as a dam between the Mediterranean and Black seas, collapsed when climatic warming at the close of the last glacial period and caused icecaps to melt, raising global sea level. With more than 200 times the force of Niagara falls, the flood caused water levels in the Black Sea, which was no more than a large lake, to rise six inches per day and swallowed 60,000 square miles in less than a year. As the Mediterranean salt water replaced fresh water, it caused a wave of human migration from what had been an oasis of fresh water within very arid lands--an exodus traumatic enough to be recorded in human memory as the epic of Gilgamesh and the biblical story of Noah's Ark, the scientists said.

"Our research is causing a re-look at the role climate plays in human history," said Ryan. "Before our work, archaeologists were focused more on studying ancient peoples' behavior based on the tools found in digs, not the bigger picture of climate change. Right now we have a working hypothesis that answers all the evidence, and we have set the stage for a good dialogue."

The scientists base much of their findings on a 1993 expedition to the Black Sea with the Russian Academy of Sciences. Though sediment cores had previously been taken from the middle of the Black Sea, the 1993 trip was the first post-Iron Curtain cruise, and the first time shoreline research was open to the West.

Using cutting-edge sonar equipment to map the ancient shoreline, Ryan and Pitman found that the shores had been at least 140 meters lower than the present shoreline. They also found a single, uniform layer of mud that strongly indicated a flood. When the sediment core samples were brought to the surface, Candace Major, a student intern for the cruise who is now a graduate student at Lamont, discovered sun-bleached freshwater mollusks, fossilized plant roots and cracks in the buried mud indicating that it had once been dried out and windswept.

"We came back with the goods," said Pitman.

While the scientists waited for the mollusk shell carbon-14 dates from an accelerated mass spectrometer--a machine with the highest accuracy available--they knew that those dates would be the ultimate test. If the sea had grown slowly for more than a thousand years, so would the population of the mollusks. But if a flood had occurred, all the mollusks would be approximately the same age.

In February 1994, the results came in. There was only a 40 year difference between the mollusks in the deepest layers and the ones in the shallowest. The date was 5,600 B.C.-- within the era of modern human history.

"Statistically, the dates were the same. It was pretty persuasive," said Pitman.

So with the scientific story in place, Ryan and Pitman began looking at other aspects of the story. They consulted with archeologists, anthropologists, linguists and seed geneticists. From this research, their hypothesis took shape: the Black Sea was an oasis where people from surrounding areas migrated during a cold, arid period beginning in 6,200 B.C. and exchanged languages, ideas and farming. When the Bosporus dam broke and the valley was deluged, the scientists believe, the peoples migrated to higher lands, taking the farming and cultural adaptations with them. The memory of the flood continued in an oral tradition for three thousand years until written languages emerged, and the tale remains in the epic of Gilgamesh and the biblical story of Noah.

"Whether or not it is true that the myths are based in the flood we discovered, the book is shaping an agenda in archeological circles," said Ryan.

Previous to Ryan and Pitman's research, the Black Sea was not a place many archeologists believed held much human history. Now, archeologists are wondering if climate change might have been the piece missing from the early human history of the region.

"This is just what we wanted to happen," said Ryan. "We wanted our research to drive the mission to have people explore the region and to look at global climate change as an important factor."